Aerobic Denitrification Process Research Articles

Potential for aerobic NO2- reduction and corresponding key enzyme genes involved in Alcaligenes faecalis strain NR.

The potential for aerobic NO2- removal by Alcaligenes faecalis strain NR was investigated. 35mg/L of NO2--N was removed by strain NR under aerobic conditions in the presence of NH4+. 15N-labeling experiment demonstrated that N2O and N2 were possible products during the aerobic nitrite removal process by strain NR. The key enzyme genes of nirK, norB and nosZ, which regulate the aerobic nitrite denitrification process, were successfully amplified from strain NR. The gene sequence analysis indicates that copper-containing nitrite reductase (NIRK) and periplasmic nitrous oxide reductase (NOSZ) were both hydrophilic protein and the transmembrane structures were absent, while nitric oxide reductase large subunit (NORB) was a hydrophobic and transmembrane protein. According to the three-dimensional structure and binding site analysis, the bulky and hydrophobic methionine residue proximity to the nitrite binding sites of NIRK was speculated to be related to the oxygen tolerance of NIRK from strain NR.

Characterization and Strain Improvement of Aerobic Denitrifying EPS Producing Bacterium Bacillus cereus PB88 for Shrimp Water Quality Management

A bacterial strain PB88 was isolated from intensive shrimp culture pond to study the denitrification process. On the basis of 16S rDNA analysis, strain PB88 was identified as Bacillus cereus PB88. It has the potential to remove 82.33 ± 3.24% $${\text{NO}}_{2}^{ - } {-} {\text{N}}$$ in synthetic medium. The optimum pH, temperature and dissolved oxygen for the highest denitrification process of the PB88 were 8.0, 30 °C and 5.21 mg/l (150 rpm) respectively. PB88 harbour the genetic sequence of nitrite reductase (nirS) enzyme which is essential to complete aerobic denitrification process. One remarkable finding is that the experimental organism produced exopolysaccharide (EPS) during the denitrification process and EPS has the antibacterial property against shrimp pathogen Vibrio harveyi MTCC 7954 (inhibition zone of 5.21 mm) and Vibrio vulnificus MTCC 1145 (inhibition zone of 7.11 mm). Removal of $${\text{NO}}_{2}^{ - } {-} {\text{N}}$$ in open base shrimp wastewater system were recorded as 98.51% by B. cereus PB88 and average shrimp body weight gained in treated system as 6 ± 0.54 to 8 ± 0.74 g within 7 days. Overall result indicated that B. cereus PB88 has the immense potential for the application in commercial shrimp culture as denitrifying agent.

Effect of NaCl on aerobic denitrification by strain Achromobacter sp. GAD-3.

This paper presents the effect of NaCl on aerobic denitrification by a novel aerobic denitrifier strain Achromobacter sp. GAD-3. Results indicated that the aerobic denitrification process was inhibited by NaCl concentrations ≥20gL-1, leading to lower nitrate removal rates (1.67∼4.0mgL-1h-1), higher nitrite accumulation (50.2∼87.4mgL-1), and increasing N2O emission ratios (13∼72mgL-1/mgL-1). Poor performance of aerobic denitrification at high salinity was attributed to the suppression of active microbial biomass and electron donating capacity of strain GAD-3. Further studies on the corresponding inhibition of the denitrifying gene expression by higher salinities revealed the significant sensitivity order of nosZ (for N2O reductase) > cnorB (for NO reductase) ≈ nirS (for cytochrome cd(1) nitrite reductase) > napA (for periplasmic nitrate reductase), accompanied with a time-lapse expression between nosZ and cnorB based on reverse transcription and real-time quantitative polymerase chain reaction (RT-qPCR) analysis. The insights into the effect of NaCl on aerobic denitrification are of great significance to upgrade wastewater treatment plants (WWTPs) containing varying levels of salinity.

Aerobic and heterotrophic nitrogen removal by Enterobacter cloacae CF-S27 with efficient utilization of hydroxylamine

Heterotrophic bacterium, Enterobacter cloacae CF-S27 exhibited simultaneous nitrification and aerobic denitrification in presence of high concentration of hydroxylamine. With the initial nitrogen concentration of 100mgL−1h−1, ammonium, nitrate and nitrite removal efficiencies were 81%, 99.9% and 92.8%, while the corresponding maximum removal rates reached as high as 11.6, 15.1 and 11.2mgL−1h−1 respectively. Quantitative amplification by real time PCR and enzyme assay demonstrated that hydroxylamine reductase gene (hao) is actively involved in hetrotrophic nitrification and aerobic denitrification process of Enterobacter cloacae CF-S27. PCR primers were designed targeting amplification of hao gene from diversified environmental soil DNA. The strain Enterobacter cloacae CF-S27 significantly maintained the undetectable amount of dissolved nitrogen throughout 60days of zero water exchange fish culture experiment in domestic wastewater.

Biopotentiality of Bacillus cereus PB45 for nitrogenous waste detoxification in ex situ model

A bacterial strain PB45 was isolated from an intensive shrimp culture pond, and its nitrification capability was studied. On the basis of 16S ribosomal DNA (rDNA) analysis, strain PB45 was identified as Bacillus cereus PB45. PB45 has the potential to remove $$ {NH}_4^{+}-\mathrm{N} $$ , $$ {\mathrm{NO}}_3^{-}-\mathrm{N} $$ , and $$ {\mathrm{NO}}_2^{-}-\mathrm{N} $$ at the rates of 66.6, 79.4, and 50%, respectively. The optimum pH, temperature, and dissolved oxygen for the highest nitrification process of the PB45 were 8.0, 30 °C, and 6.68 mg/l (200 rpm), respectively. PB45 could express periplasmic nitrate reductase (napA), hydroxylamine oxidoreductase (hao), and nitrite reductase (nirS) which are essential to complete heterotrophic nitrification and aerobic denitrification process. Removal of $$ {NH}_4^{+}-\mathrm{N} $$ , $$ {\mathrm{NO}}_3^{-}-\mathrm{N} $$ , and $$ {\mathrm{NO}}_2^{-}-\mathrm{N} $$ in an aquarium base shrimp wastewater system was recorded to be 99.76, 99.37, and 99.72%, respectively, by PB45. This result indicated that PB45 has the prospect for future full-scale application in commercial shrimp culture.

Removal of nitrogen and phosphorus by heterotrophic nitrification-aerobic denitrification of a denitrifying phosphorus-accumulating bacterium Enterobacter cloacae HW-15

A new denitrifying phosphorus-accumulating bacterium HW-15 was screened out from phosphorus-rich wastewater and was identified as Enterobacter cloacae sp. based on its physiological-biochemical characteristics and 16S rDNA sequence analysis. The shift in microbial community structure during acclimation was determined through high-throughput sequencing and Enterobacter was found to be the dominant genus. Strain HW-15 exhibited efficient simultaneous denitrifying and phosphorus removal, and achieved both heterotrophic nitrification and aerobic denitrification process, and demonstrated a preference for consuming nitrogen sources in order of NH+ 4-N>NO- 3-N>NO- 2-N. The application of strain HW-15 in real wastewater samples resulted in NH+ 4-N, NO- 3-N, NO- 2-N and PO3- 4-P removal efficiencies of 99%, 88%, 59%, and 73%, respectively. Besides, strain HW-15 was found to simultaneously remove nutrient and arsenic(V) at an arsenic(V) concentration lower than 1.5mg/L. During anaerobic-aerobic culture period, the polyhydroxyalkanoate (PHA) content in HW-15 cells presented a dynamic change, and resulted in PO3- 4-P removal efficiency of 61.97%. Strain HW-15 could process NH+ 4-N to NO- 2-N and then to gaseous nitrogen.

Effects of temperature on aerobic denitrification in a bio-ceramsite reactor

ABSTRACTAn aerobic denitrifying bacteria Pseudomonas sp. Z31 was added to a bio-ceramsite reactor to treat nitrate polluted wastewater. The purpose of this work was to investigate the effects of temperature on aerobic denitrification process in the reactor. When temperature increased from 15 to 30°C, nitrate (NO3–-N) removal efficiency increased from 66.20 to 98.79%, total nitrogen (TN) removal efficiency increased from 61.34 to 96.76%, and chemical oxygen demand (COD) removal efficiency increased from 78.08 to 92.82%. In addition, large numbers of reported aerobic denitrifying bacteria such as Bacillus sp. and Pseudomonas sp. were detected in the bio-ceramsite reactor.

Simultaneous bisphenol F degradation, heterotrophic nitrification and aerobic denitrification by a bacterial consortium

AbstractBACKGROUNDTraditional aerobic autotrophic nitrification and anoxic heterotrophic denitrification have many limitations. Recently, the simultaneous heterotrophic nitrification–aerobic denitrification (HN‐AD) process has received increasing attention. Thus, the possibility of the simultaneous removal of bisphenols and NH4+‐N via HN‐AD was investigated.RESULTSA bisphenols‐degrading bacterial consortium was enriched and capable of degrading 50 mg L−1 bisphenol A, 300 mg L−1 4,4‐dihydroxybenzophenone, 375 mg L−1 bisphenol F (BPF) and 10 mg L−1 bis(4‐hydroxyphenyl)sulfide under aerobic conditions. Further studies showed that the bacterial consortium could completely degrade 300 mg L−1 BPF and remove NH4+‐N at 35 °C with 150 rpm at the C/N ratio of over 10. Moreover, BPF mineralization and NH4+‐N reduction to N2 were observed. Clone library analysis indicated that Salmonella enterica, Enterobacter,Citrobacter and Pseudomonas could cooperate to degrade BPF and reduce NH4+‐N to N2. Among these species, the isolated Pseudomonas sp. HS‐2 was capable of simultaneous BPF degradation and NH4+‐N removal via HN‐AD.CONCLUSIONThe experimental results demonstrated that the enriched bacterial consortium and the isolated strain HS‐2 could simultaneously remove BPF and NH4+‐N via HN‐AD, indicating that this is a potential way for the treatment of wastewaters containing these compounds. © 2016 Society of Chemical Industry

Mathematical simulating the process of aerobic granular sludge treating high carbon and nitrogen concentration wastewater

The Activated Sludge Model No. 3 (ASM3) was modified by considering the simultaneous storage and growth, heterotrophic nitrification and aerobic denitrification processes. The model was used to simulate the biological process of aerobic granular sludge (AGS) treating high COD and nitrogen piggery wastewater without any pretreatment. In the model, the AGS utilizes readily biodegradable substrates for simultaneous storage, growth and metabolism during the feast phase. It further utilizes storage products for secondary growth and metabolism during the famine phase. Finally, it produces inert organic carbon through the decay. For nitrogen removal, nitrification process is mainly heterotrophic nitrification. Denitrification is completed by a combined process of anoxic and aerobic denitrification. The comparison between simulation results and experimental data shows that the modified model satisfactorily simulated the organic substrates degradation, nitrification and denitrification processes of treatment of high-concentration piggery wastewater by AGS.

An adsorption-release-biodegradation system for simultaneous biodegradation of phenol and ammonium in phenol-rich wastewater

The feasibility of simultaneous biodegradation of phenol and ammonium in phenol-rich wastewater was evaluated in a reusable system, which contained macroporous adsorption resin and Alcaligenes faecalis strain WY-01. In the system, up to 6000mg/L phenol could be completely degraded by WY-01; meanwhile, 99.03±3.95% of ammonium was removed from the initial concentration of 384mg/L. This is the first study to show the capability of single strain in simultaneous removal of ammonium and phenol in wastewater containing such high concentrations of phenol. Moreover, the resin was regenerated during the biodegradation process without any additional manipulations, indicating the system was reusable. Furthermore, enzyme assay, gene expression patterns, HPLC–MS and gas chromatography analysis confirmed that phenol biodegradation accompanied with aerobic nitrifier denitrification process. Results imply that the reusable system provides a novel strategy for more efficient biodegradation of phenol and ammonium contained in some particular industrial wastewater.

Marinobacter strain NNA5, a newly isolated and highly efficient aerobic denitrifier with zero N2O emission

An efficient aerobic denitrification bacterium, strain NNA5, was isolated and identified as Marinobacter sp. NNA5. NNA5 did not perform heterotrophic nitrification. GC/IRMS analysis revealed that 15N2 was produced from Na15NO2 and K15NO3. GC/MS and quantitative analyses showed that no N2O emission occurred when nitrite or nitrate was used as substrate. Single factor experiments indicated that optimal conditions for aerobic denitrification were: sodium succinate or sodium pyruvate as carbon source, temperature 35°C, NaCl concentration 2–4%, C/N ratio 6–8, pH 7.5, rotation speed 150rpm (giving dissolved oxygen concentration 6.08mg/L), NO3−-N concentration ranging from 140 to 700mg/L. NNA5 displayed highly efficient aerobic denitrifying ability, with maximal NO3−-N removal rate 112.8mg/L/d. In view of its ability to perform aerobic denitrification with zero N2O emission, NNA5 has great potential for future application in aerobic denitrification processes in industrial and aquaculture wastewater treatment systems.

Characteristics of a Novel Aerobic Denitrifying Bacterium, Enterobacter cloacae Strain HNR

A novel aerobic denitrifier strain HNR, isolated from activated sludge, was identified as Enterobacter cloacae by16S rRNA sequencing analysis. Glucose was considered as the most favorable C-source for strain HNR. The logistic equation well described the bacterial growth, yielding a maximum growth rate (μmax) of 0.283h(-1) with an initial NO3 (-)-N concentration of 110mg/L. Almost all NO3 (-)-N was removed aerobically within 30h with an average removal rate of 4.58mgNL(-1)h(-1). Nitrogen balance analysis revealed that proximately 70.8% of NO3 (-)-N was removed as gas products and only 20.7% was transformed into biomass. GC-MS result indicates that N2 was the end product of aerobic denitrification. The enzyme activities of nitrate reductase and nitrite reductase, which are related to the process of aerobic denitrification, were 0.0688 and 0.0054 U/mg protein, respectively. Thus, the aerobic denitrification of reducing NO3 (-) to N2 by strain HNR was demonstrated. The optimal conditions for nitrate removal were C/N ratio 13, pH value 8, shaking speed 127rpm and temperature 30°C. These findings show that E. cloacae strain HNR has a potential application on wastewater treatment to achieve nitrate removal under aerobic conditions.

Genetic associations as indices of nitrogen cycling rates in an aerobic denitrification biofilter used for groundwater remediation

An aerobic denitrification biofilter (ADB) for groundwater remediation was developed with high removal efficiencies (total nitrogen (TN): 82.3–95.8%; NO3−-N: 93.2–98.2%). Nitrate (NO3−-N) transformation rates stabilized between 21.0 and 23.4g/(m3h), whereas nitrite (NO2−-N) and ammonium (NH4+-N) transformation rates remained less than 6.0g/(m3h) as the dissolved oxygen (DO) level increased from 1.0mg/L to 6.0mg/L. Nitric oxide (NO) and nitrous oxide (N2O) accumulated with great fluctuations (NO: 0–1.6×10−3g/(m3h); N2O: 0.1–1.1g/(m3h)) throughout the experiment. This study suggested that gene associations reflect quantitative relationships with aerobic denitrification rates and can provide useful information regarding aerobic denitrification processes in groundwater. Especially, the qnorB/nosZ ratio acts as the main driver for NO3−-N and NH4+-N transformation, while the qnorB/nosZ ratio followed by the (nirS+nirK)/nosZ ratio serve a dominant role in the accumulation of N2O and NO.

Effect of temperature downshifts on biological nitrogen removal and community structure of a lab-scale aerobic denitrification process

Aerobic denitrification bacteria are currently being explored as promising microorganisms with which to treat wastewater containing concentrated ammonium and organic carbon at psychrophilic temperatures. However, little is know regarding the mixed culture of these microbes under low-temperature shocks. In this study, a lab-scale aerobic denitrifying process was established in a sequencing bioreactor at 25°C, and successfully performed in a short-term temperature downshift period that ranged from 25°C to 5°C. The specific aerobic denitrification rate was maximized at 15°C [15.33mg N/(gSSh)], and this process effectively removed chemical oxygen demand (COD) and nitrate (above 90%) even at 5°C. The results of Illumina MiSeq 16S rRNA amplicon analysis revealed a relatively stable microbial community across the transitional periods of temperature. Pseudomonas was the most abuntant genus below 15°C, and the amount of species Pseudomonas alcaligenes significantly increased at 5°C with potassium nitrate as the primary nitrogen source. The communities of aerobic denitrifying bacteria in the temperature downshift period were all highly organized functionally, and they were relatively stably across the temperature gradient. These results will enhance understanding regarding the microbial ecology of aerobic denitrifiers in mixed cultures, leading to a more effective controlling of aerobic denitrification process during temperature transition states.

Efficient aerobic denitrification in the treatment of leather industry wastewater containing high nitrogen concentration

To treat leather industry wastewater (LIW) containing high nitrogen concentration, eight aerobic denitrifiers were isolated from sludge existing in an LIW-treatment aeration tank. Among them, one strain named as KH8 had showed the great ability in denitrification under an aerobic condition, and it was identified as Pseudomonas aeruginosa R12. The aerobic denitrification ability of the strain KH8 was almost comparable to its anaerobic denitrification ability. In lab-scale aerobic denitrifications performed in 1-L five-neck flasks for 48 hr, denitrification efficiency was found to be much improved as the strain KH8 held a great majority in the seeded cells. From the nitrogen balance at the cell-combination ratio of 10:1 (the strain KH8 to the other seven isolates) within the seeded cells, the percentage of nitrogen loss during the aerobic denitrification process was estimated to be 58.4, which was presumed to be converted to N2 gas. When these seeded cells with lactose were applied to plant-scale aeration tank for 56 day to treat high-strength nitrogen in LIW, the removal efficiencies of CODCr and TN were achieved to be 97.0% and 89.8%, respectively. Under this treatment, the final water quality of the effluent leaving the treatment plant was good enough to meet the water-quality standards. Consequently, the isolated aerobic denitrifiers could be suitable for the additional requirement of nitrogen removal in a limited aeration-tank capacity. To the best of our knowledge, this is the first report of aerobic denitrifiers applied to plant-scale LIW treatment.

Interaction of Cr(VI) reduction and denitrification by strain Pseudomonas aeruginosa PCN-2 under aerobic conditions

Inhibition of efficient denitrification in presence of toxic heavy metals is one of the current problems encountered in municipal wastewater treatment plants. This paper presents how to remove hexavalent chromium (Cr(VI)) and nitrate simultaneously by the novel strain Pseudomonas aeruginosa PCN-2 under aerobic conditions. The capability of strain PCN-2 for Cr(VI) and nitrate reduction was confirmed by PCR analysis of gene ChrR, napA, nirS, cnorB, nosZ, while Cr(VI) reduction was proved via an initial single-electron transfer through Cr(V) detection using electron paramagnetic resonance. Experimental results demonstrated that Cr(VI) and nitrate reduction by strain PCN-2 was much faster at pH 8–9 and higher initial cell concentration. However, increasing Cr(VI) concentration would inhibit aerobic denitrification process and result in an significant delay of nitrate reduction or N2O accumulation, which was attributed to competition between three electron acceptors, i.e., Cr(VI), O2 and nitrate in the electron transport chain.

Screening and Characterization of a Bacterium Capable of Simultaneous Heterotrophic Nitrification and Aerobic Denitrification at High Concentrations of Ammonia-Nitrogen

A bacterium capable of simultaneous heterotrophic nitrification and aerobic denitrification at high concentrations of ammonia-nitrogen was screened and identified and the denitrification property was investigated in this paper. The strain was isolated from aeration tank of wastewater disposed by activated sludge and analyzed and identified by 16S rDNA. The effects of different carbon sources and carbon and nitrogen mass ratios on denitrification rate were studied. The changes of various forms of ammonia-nitrogens during the simultaneous heterotrophic nitrification and aerobic denitrification process were characterized. A strain capable of simultaneous heterotrophic nitrification and aerobic denitrification at 600 mg/L nitrogen concentration has been isolated and screened. Comparison of its 16S rDNA sequence showed 100% similarity to Bacillus licheniformis strain Lr124/6. The strain was named as Bacillus sp. A22. The optimal conditions for degradation of ammonia-nitrogen by Bacillus sp. A22 were trisodium citrate as carbon source and carbon and nitrogen mass ratios of 10. The denitrification rate was 98.2% after 96 h of culture under the optimal conditions and there was hardly any intermediates accumulation in the denitrification process. It has practical applications that the denitrification can be performed efficiently at high concentrations of ammonia-nitrogen by method of simultaneous heterotrophic nitrification and aerobic denitrification by Bacillus sp. A22 in nitrogen purification treatment of wastewater with high concentrations of ammonia-nitrogen.

Identification of a Highly Efficient Aerobic Denitrifying Bacterium in SBR and Denitrification Optimization

Aerobic denitrification process is attracted more attention to enhance nitrogen removal technology. Aerobic denitrifying bacteria present excelled abilities with fast growth rate and denitrifying speed, though they are not dominant in most practical processes. A high-efficiency strain was enriched in SBR from aerobic activated sludge by the way of intermittent aeration and continuous aeration combination. The strain was determined to Pseudomonasstutzeri T13 with ability of TN removal 90% and nitrate removal 97%. The limiting factors for aerobic denitrifying efficiency were optimized to temperature=31°C,pH=7.11 and DO=2.5 mg/L using response surface methodology. A total of 32 genes are related to nitrogen removal in strain T13. And 10 related to nitrate reductase, especially including 3 genes encoding the periplasmic nitrate reductase, playing important role to aerobic denitrification. It gave good understanding to supply effective technological supports for aerobic denitrification process.

Model-based evaluations of operating parameters on CANON process in a membrane-aerated biofilm reactor

Abstract Nitrogen compounds, such as ammonium, naturally appear in most wastewaters necessitating treatment in order to prevent oxygen depletion and eutrophication of surface water bodies. Conventional biological nitrogen removal from wastewater usually performed using possible set-ups of sequential aerobic nitrification and anoxic denitrification processes. The completely autotrophic nitrogen removal over nitrite (CANON) process is a combination of partial nitrification an Anaerobic Ammonia Oxidation (ANAMMOX) in which the aerobic ammonium oxidizers and ANAMMOX bacteria perform two sequential reactions under oxygen-limited conditions. CANON process is suitable to remove ammonium from wastewaters characterized by the low content of organic carbon yet abundance of ammonium. It performs with limited volume and reasonable budget; hence, any available nitrification unit might be converted into a new improved one rather easily while benefiting from flexibility of CANON control strategies. To better understand ...

Isolation of an Aerobic Denitrifying Bacterial Strain from a Biofilter for Removal of Nitrogen Oxide

A strain of bacteria CP1 with high nitrogen removal efficiency was newly isolated from the biofilm of a biofilter for removal of NOx from flue gas. The isolate was identified as Pseudomonas aeruginosa based on its physiological and biochemical characteristics and the results of 16S rRNA gene homology analysis. The new isolate had a high denitrifying ability, removing 98.49% of the nitrate in a 24-h period under aerobic conditions, with no nitrite accumulation. With regard to the nitrogen balance, the percentage of nitrogen lost in the flask culture was estimated to be 32.3%, which was presumed to be converted to nitrogen gas. An analysis of its denitrification activity showed that the optimal C/N and temperature were 12 and 30°C-40°C, respectively. By using glucose, sodium citrate and succinate, CP1 removed nitrate with high denitrification efficiency. The change in DO did not influence the effects of denitrification when it varied from 0 to 7.2 mg/L. The results show that CP1 could be a good candidate for the process of aerobic denitrification.